EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH CERN-PH-EP-2010-002 17 January 2010 Observation of a VHE Cosmic-Ray Flare-Signal with the L 3 + C Muon Spectrometer The L 3 + C Collaboration

The data collected by the L3+C muon spectrometer at the CERN Large ElectronPositron collider, LEP, have been used to search for short duration signals emitted by cosmic point sources. A sky survey performed from July to November 1999 and from April to November 2000 has revealed one single flux enhancement (chance probability = 2.6·10) between the 17th and 20th of August 2000 from a direction with a galactic longitude of (265.02 ± 0.42) and latitude of (55.58 ± 0.24). The energy of the detected muons was above 15 GeV. Reference: Astroparticle Physics, 33 (2010 )24 − 39